Storage device, storage apparatus, magnetic head, and electronic apparatus

ABSTRACT

[Object] To provide a storage device that realizes both a high information retention property and a low power consumption. 
     [Solving Means] A storage device includes a fixed layer, a storage layer, an intermediate layer, and a heat generation layer. The fixed layer includes a first ferromagnetic layer that includes a fixed perpendicular magnetization. The storage layer includes a second ferromagnetic layer that includes a perpendicular magnetization invertible by a spin injection. The intermediate layer is formed of an insulator and is arranged between the storage layer and the fixed layer. The heat generation layer is formed of a resistance heating element and is arranged in at least one of the storage layer and the fixed layer. With this configuration, it becomes possible to provide a storage device that realizes both a high information retention property and a low power consumption.

TECHNICAL FIELD

The present technology relates to a storage device, a storage apparatus,a magnetic head, and an electronic apparatus that perform recordingusing a spin torque magnetization inversion.

BACKGROUND ART

In various electronic apparatuses such as a computer, a DRAM (DynamicRandom Access Memory) that can be operated at high speed and is capableof recording information with a high density is widely used as a storageapparatus. However, in recent years, a nonvolatile memory that retainsrecorded information even when power is turned off is starting to beused in various fields in place of the DRAM which is a volatile memoryin which recorded information is deleted when power is turned off.

An MRAM (Magnetoresistive Random Access Memory) is known as thenonvolatile memory capable of recording at high speed. As the MRAM, aconfiguration that uses a giant magneto resistive (GMR: Giant MagnetoResistive) device and a configuration that uses a magnetic tunneljunction (MTJ: Magnetic Tunnel Junction) device are known.

The MRAM that uses the MTJ device is called STT (Spin TransferTorque)-MRAM. Since the STT-MRAM includes a higher magnetoresistancechange rate (MR ratio) than the MRAM that uses a GMR device,high-intensity readout signals can be generated. Technologies related tothe STT-MRAM are disclosed in, for example, Patent Literatures 1 to 4and Non-patent Literatures 1 to 4.

As an STT-MRAM recording system, there are an in-plane magnetizationsystem and a perpendicular magnetization system in which magnetizationdirections mutually differ between MTJ devices. In recent years, anSTT-MRAM of a perpendicular magnetization system, that can be made morecompact and set to have a large capacity is attracting attention. In arecording operation of the STT-MRAM of a perpendicular magnetizationsystem, by performing a spin injection by causing a current to flowthrough each MTJ device, a perpendicular magnetization of a storagelayer in each of the MTJ devices is inverted. In the STT-MRAM, binaryinformation (typically, “0” and “1”) can be recorded on the basis ofdirections of the perpendicular magnetizations in the MTJ devices.

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent Application Laid-open No.    2003-17782-   Patent Literature 2: Specification of U.S. Pat. No. 6,256,223-   Patent Literature 3: Specification of US Patent Application    Publication No. 2005/0184839A1-   Patent Literature 4: Japanese Patent Application Laid-open No.    2008-227388

Non-Patent Literature

-   Non-Patent Literature 1: PHYs. Rev. B, 54.9353 (1996)-   Non-Patent Literature 2: J. Magn. Mat., 159, L1 (1996)-   Non-Patent Literature 3: F. J. Albert et al., Appl. Phy. Lett., 77,    3809 (2000)-   Non-Patent Literature 4: Nature Materials., 5, 210 (2006)

DISCLOSURE OF INVENTION Technical Problem

In the STT-MRAM of a perpendicular magnetization system, a higherinformation retention property with which recorded information can beretained more stably can be obtained as a stability of the perpendicularmagnetization in the MTJ devices becomes higher. Meanwhile, since theperpendicular magnetization becomes more difficult to be inverted as thestability of the perpendicular magnetization in the MTJ devices becomeshigher, a large current becomes necessary for inverting theperpendicular magnetization during a recording operation. In this way,in the STT-MRAM, the information retention property and powerconsumption are in a mutual tradeoff relationship, and a technique forrealizing them both is being desired.

In view of the circumstances as described above, the present technologyaims at providing a storage device, a storage apparatus, a magnetichead, and an electronic apparatus that realize both a high informationretention property and low power consumption.

Solution to Problem

For attaining the object described above, a storage device according toan embodiment of the present technology includes a fixed layer, astorage layer, an intermediate layer, and a heat generation layer.

The fixed layer includes a first ferromagnetic layer that includes afixed perpendicular magnetization.

The storage layer includes a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection.

The intermediate layer is formed of an insulator and is arranged betweenthe storage layer and the fixed layer.

The heat generation layer is formed of a resistance heating element andis arranged in at least one of the storage layer and the fixed layer.

In the storage device having this configuration, a current flows throughthe heat generation layer formed of a resistance heating element due toa spin injection during a recording operation, and Joule heat is thusgenerated, so a temperature of the second ferromagnetic layer of thestorage layer increases. Therefore, by the temperature of the secondferromagnetic layer rising only at an instant of the recordingoperation, the stability of the perpendicular magnetization of thesecond ferromagnetic layer is lowered, and it becomes easier for theperpendicular magnetization of the second ferromagnetic layer to beinverted. Accordingly, recording operations of low power consumptionbecome possible in the storage device.

On the other hand, in the storage device, the second ferromagnetic layerof the storage layer returns to an ambient temperature (typically, roomtemperature) after the recording operation, and the stability of theperpendicular magnetization of the second ferromagnetic layer returns tothe high state. In other words, while the stability of the perpendicularmagnetization of the second ferromagnetic layer is lowered for a momentduring the recording operation, the stability is maintained high atother times. Therefore, a high information retention property isobtained in the storage device.

In this way, in the storage device, both the high information retentionproperty and low power consumption can be realized.

Further, the storage device is insusceptible to a heat load appliedthereto in a production process of a storage apparatus including thestorage device or a process of mounting the storage apparatus ontovarious electronic apparatuses. Specifically, in the storage device, aninfluence of a heat load on the perpendicular magnetization of the firstferromagnetic layer of the fixed layer and the perpendicularmagnetization of the second ferromagnetic layer of the storage layer issuppressed by heat resistance of the heat generation layer formed of aresistance heating element. Therefore, since a perpendicular magneticanisotropy of the first ferromagnetic layer and the second ferromagneticlayer is difficult to be impaired in the storage device, high recordingperformance is secured.

The heat generation layer may be arranged in at least the storage layer.

In the storage device including this configuration, since the heatgeneration layer is arranged close to the second ferromagnetic layer,the temperature of the second ferromagnetic layer is apt to increaseduring the recording operation. Accordingly, recording operations oflower power consumption become possible.

The heat generation layer may be adjacent to the first ferromagneticlayer or the second ferromagnetic layer.

In the storage device including this configuration, the influence of aheat load on the perpendicular magnetizations of the first ferromagneticlayer and the second ferromagnetic layer is effectively suppressed bythe heat resistance of the heat generation layer adjacent to the firstferromagnetic layer and the second ferromagnetic layer. Moreover, in acase where the heat generation layer is adjacent to the secondferromagnetic layer, the temperature of the second ferromagnetic layerbecomes more apt to increase during the recording operation, sorecording operations of lower power consumption become possible.

The resistance heating element may be configured by at least one of anitride, carbide, boride, oxide, elemental carbon, and elemental boronand include an electrical resistivity of 1 Ωm or more and 1*10⁴ Ωm orless at 20° C.

The heat generation layer may have a thickness of 0.2 nm or more and 2.0nm or less.

In the heat generation layer formed of such a resistance heatingelement, Joule heat can be generated more effectively, and an effect ofmaintaining the perpendicular magnetic anisotropy of the firstferromagnetic layer and the second ferromagnetic layer can be obtainedmore favorably.

The first ferromagnetic layer and the second ferromagnetic layer may beformed of a metal including at least one of Co, Fe, and Ni as a maincomponent or a boron alloy including at least one of Co, Fe, and Ni andB.

The first ferromagnetic layer and the second ferromagnetic layer may beformed of a material including at least one of V, Cr, Nb, Mo, Ta, W, Hf,Zr, Ti, and Ru as an accessory component.

In the storage device including this configuration, it becomes possibleto form a favorable perpendicular magnetization in the firstferromagnetic layer of the fixed layer and the second ferromagneticlayer of the storage layer, and high recording performance can thus beobtained.

The fixed layer may further include two first ferromagnetic layers and anonmagnetic layer arranged between the two first ferromagnetic layers.

At least one of the two first ferromagnetic layers may be formed of amaterial including at least one of Co, Fe, and Ni and at least one ofPt, Pd, Rh, and Ni as main components.

One of the two first ferromagnetic layers may be formed of a materialincluding at least one of Co, Fe, and Ni and at least one of Pt, Pd, Rh,and Ni as main components, and the other one of the two firstferromagnetic layers may be formed of a metal including at least one ofCo, Fe, and Ni as a main component or a boron alloy including at leastone of Co, Fe, and Ni and B.

In the storage device including this configuration, by configuring thefixed layer in a so-called laminated ferrimagnetic structure, a leakfield in the fixed layer can be suppressed, so it becomes possible toprevent the storage layer from being influenced by the leak field.

The insulator may be configured by MgO.

Since a magnetoresistance change rate (MR ratio) increases in thestorage device including this configuration, recording operations of lowpower consumption becomes possible.

The storage device may further include a cap layer adjacent to thestorage layer on a side opposite to the intermediate layer.

The cap layer may include a metal layer including any one of Hf, Ta, W,Zr, Nb, Mo, Ti, Mg, V, Cr, Ru, Rh, Pd, and Pt as a main component.

The cap layer may further include an oxide layer including any one ofMgO, Al₂O₃, and SiO₂ as a main component.

In the storage device including this configuration, by covering thestorage layer by the cap layer, an oxidization of the storage layer canbe prevented from occurring.

The storage device may further include a base layer adjacent to thefixed layer on a side opposite to the intermediate layer.

The base layer may include a plurality of layers that include any one ofTa, Ti, Cu, TiN, TaN, NiCr, NiFeCr, Ru, and Pt as a main component.

In the storage device including this configuration, it becomes possibleto control crystallization of the fixed layer adjacent to the base layeras well as causing the base layer to function as an electrode.

A storage apparatus according to an embodiment of the present technologyincludes a plurality of storage devices and a wiring unit configured tobe capable of supplying a current to each of the plurality of storagedevices.

The plurality of storage devices include a fixed layer, a storage layer,an intermediate layer, and a heat generation layer.

The fixed layer includes a first ferromagnetic layer that includes afixed perpendicular magnetization.

The storage layer includes a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection.

The intermediate layer is formed of an insulator and is arranged betweenthe storage layer and the fixed layer.

The heat generation layer is formed of a resistance heating element andis arranged in at least one of the storage layer and the fixed layer.

A magnetic head according to an embodiment of the present technologyincludes a magnetic device including a fixed layer, a storage layer, anintermediate layer, and a heat generation layer.

The fixed layer includes a first ferromagnetic layer that includes afixed perpendicular magnetization.

The storage layer includes a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection.

The intermediate layer is formed of an insulator and is arranged betweenthe storage layer and the fixed layer.

The heat generation layer is formed of a resistance heating element andis arranged in at least one of the storage layer and the fixed layer.

An electronic apparatus according to an embodiment of the presenttechnology includes a storage unit including a plurality of storagedevices and a control unit configured to be capable of accessing thestorage unit.

The plurality of storage devices include a fixed layer, a storage layer,an intermediate layer, and a heat generation layer.

The fixed layer includes a first ferromagnetic layer that includes afixed perpendicular magnetization.

The storage layer includes a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection.

The intermediate layer is formed of an insulator and is arranged betweenthe storage layer and the fixed layer.

The heat generation layer is formed of a resistance heating element andis arranged in at least one of the storage layer and the fixed layer.

Advantageous Effects of Invention

As described above, according to the present technology, a storagedevice, a storage apparatus, a magnetic head, and an electronicapparatus that realize both a high information retention property andlow power consumption can be provided.

It should be noted that the effects described herein are not necessarilylimited, and any effect described in the present disclosure may beobtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A perspective view schematically showing a storage apparatusaccording to an embodiment of the present technology.

FIG. 2 A cross-sectional diagram of the storage apparatus taken alongthe line A-A′ of FIG. 1.

FIG. 3 A cross-sectional diagram schematically showing a storage deviceof the storage apparatus.

FIG. 4 A cross-sectional diagram schematically showing a modifiedexample of the storage device.

FIG. 5 Cross-sectional diagrams each schematically showing a modifiedexample of a storage layer of the storage device.

FIG. 6 Cross-sectional diagrams each schematically showing a modifiedexample of a fixed layer of the storage device.

FIG. 7 A cross-sectional diagram schematically showing a modifiedexample of the storage device.

FIG. 8 Cross-sectional diagrams each schematically showing a sample forevaluating the storage layer of the storage device.

FIG. 9 Diagrams showing measurement results of a magnetic property ofthe storage layer of the storage device.

FIG. 10 A diagram showing a measurement result of a magnetic property ofa storage layer according to a comparative example.

FIGS. 11 Cross-sectional diagrams each schematically showing a samplefor evaluating an information retention property of the storage deviceand an information writing current density.

FIG. 12 Diagrams schematically showing a magnetic head including thestorage apparatus.

FIG. 13 A block diagram showing a schematic configuration of anelectronic apparatus including the storage apparatus.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present technology will be describedwith reference to the drawings.

In the drawings, an X axis, a Y axis, and a Z axis orthogonal to oneanother are illustrated as appropriate. The X axis, the Y axis, and theZ axis are common throughout all the figures.

[Schematic Configuration of Storage Apparatus]

FIG. 1 is a perspective view showing a schematic configuration of astorage apparatus 20 according to an embodiment of the presenttechnology. FIG. 2 is a cross-sectional diagram of the storage apparatus20 taken along the line A-A′ of FIG. 1.

The storage apparatus 20 includes gate lines 1 as word lines extendingin an X-axis direction, bit lines 6 extending in a Y-axis direction, andstorage devices 3. The gate lines 1 and the bit lines 6 configure twotypes of address lines (wiring unit) orthogonal to one another. The bitlines 6 are provided above the gate lines 1 in a Z-axis direction.

The storage devices 3 are each arranged between the gate lines 1 and thebit lines 6 in correspondence with intersections of the gate lines 1 andthe bit lines 6. The storage devices 3 configure an STT-MRAM (SpinTransfer Torque based Magnetic Random Access Memory) of a perpendicularmagnetization system, that is capable of retaining information bydirections of perpendicular magnetizations.

The storage apparatus 20 includes a semiconductor substrate 10 thatholds the gate lines 1. Device separation areas 2, source areas 7, and adrain area 8 are provided in the semiconductor substrate 10. The deviceseparation areas 2 demarcate memory cells in the storage apparatus 20.The source areas 7 and the drain area 8 configure a selection transistorfor selecting each of the storage devices 3 together with the gate lines1. Further, a wiring 9 that extends in the X-axis direction above thedrain area 8 is provided on the semiconductor substrate 10.

A plurality of columnar contacts 4 that extend in the Z-axis directionare provided in the storage apparatus 20. The contacts 4 are formed of aconductive material such as copper, for example. The storage devices 3are connected to the source areas 7 of the semiconductor substrate 10via the contacts 4 and connected to the bit lines 6 via the contacts 4.The wiring 9 is connected to the drain area 8 via the contacts 4.

In a recording operation of the storage apparatus 20, a perpendicularmagnetization of the storage devices 3 is inverted by a spin injectionwith respect to the storage devices 3. The spin injection with respectto the storage devices 3 is performed by causing a current to flowthrough the storage devices 3 by applying a voltage between the gatelines 1 and the bit lines 6. In the storage apparatus 20, a voltage canbe applied between arbitrary gate lines 1 and bit lines 6 by theselection transistor described above, and a spin injection can beperformed with respect to arbitrary storage devices 3 in accordance withcombinations of the gate lines 1 and the bit lines 6.

It should be noted that since the selection transistor is operable witha current equal to or smaller than a saturation current, there is a needto perform the spin injection with a current equal to or smaller thanthe saturation current of the selection transistor in the recordingoperation of the storage apparatus 20. However, although details will begiven later, in the storage apparatus 20 of this embodiment, the storagedevices 3 are configured to be capable of at least performing a spininjection with a current smaller than the saturation current withrespect to the selection transistor.

[Storage Device]

(Schematic Configuration)

FIG. 3 is a cross-sectional diagram schematically showing the storagedevice 3 of the storage apparatus 20. The storage device 3 includes abase layer 31, a fixed layer 32, an intermediate layer 33, a storagelayer 34, and a cap layer 35. Each layer of the storage device 3 isformed in a form of a film that extends parallel to an XY plane.

In the storage device 3, the fixed layer 32, the intermediate layer 33,and the storage layer 34 configure a magnetic tunnel junction (MTJ:Magnetic Tunnel Junction) device. It should be noted that the MTJ deviceis also called TMR (Tunnel Magneto Resistance) device.

In the storage device 3, it is possible to realize low power consumptionand a large capacity by decreasing a dimension of the XY plane in thein-plane direction. From this viewpoint, it is favorable to make an areaof a cross section parallel to the XY plane of the storage device 3 tobe 0.01 μm² or less.

In a production process of the storage apparatus 20, the base layer 31,fixed layer 32, intermediate layer 33, storage layer 34, and cap layer35 of the storage device 3 can be formed by a series of processes withina vacuum apparatus, and the storage device 3 can be patterned by aprocessing process such as etching after that. Therefore, the storageapparatus 20 including the storage devices 3 has an advantage that itcan be produced by a general semiconductor MOS forming process.

(Fixed Layer)

The fixed layer (also called “reference layer”, “pin layer”, etc.) 32includes a first ferromagnetic layer 321 formed of a ferromagneticsubstance. It is favorable for the first ferromagnetic layer 321 to havea film thickness of 0.5 nm or more and 30 nm or less.

The first ferromagnetic layer 321 of the fixed layer 32 includes aperpendicular magnetization M32 perpendicular to the XY plane, and adirection of the perpendicular magnetization M32 is fixed. In otherwords, even when a spin injection is performed on the storage device 3,the direction of the perpendicular magnetization M32 does not change inthe first ferromagnetic layer 321. In the example shown in FIG. 3, thedirection of the perpendicular magnetization M32 of the firstferromagnetic layer 321 is an upward Z-axis direction as indicated bythe block arrow and is maintained in the upward Z-axis direction evenwhen a spin injection is performed on the storage device 3.

The ferromagnetic substance forming the first ferromagnetic layer 321 ofthe fixed layer 32 can be determined as appropriate but is favorably ametal material including at least one of Co, Fe, and Ni as a maincomponent or a boron alloy including at least one of Co, Fe, and Ni andB, for example. As an example, the first ferromagnetic layer 321 can beformed of CoFeB. Moreover, the first ferromagnetic layer 321 may includea configuration in which a plurality of layers respectively formed ofdifferent types of ferromagnetic substances are directly laminated ontop of one another.

(Storage Layer)

The storage layer (also called “freedom layer”, “free layer”, etc.) 34includes a second ferromagnetic layer 341 formed of a ferromagneticsubstance and a heat generation layer 342 formed of a resistance heatingelement. The storage layer 34 is provided above and opposes the fixedlayer 32 in the Z-axis direction. It is favorable for the secondferromagnetic layer 341 to have a film thickness of 0.5 nm or more and30 nm or less.

The second ferromagnetic layer 341 of the storage layer 34 includes aperpendicular magnetization M34 perpendicular to the XY plane, and theperpendicular magnetization M34 can be inverted by a spin injection. Inother words, as a spin injection is performed on the storage device 3, adirection of the perpendicular magnetization M34 becomes a directioncorresponding to a spin torque of electrons in the second ferromagneticlayer 341. In the example shown in FIG. 3, the direction of theperpendicular magnetization M34 of the second ferromagnetic layer 341can be inverted from the upward Z-axis direction to a downward Z-axisdirection or from the downward Z-axis direction to the upward Z-axisdirection by the spin injection to the storage device 3.

The ferromagnetic substance forming the second ferromagnetic layer 341of the storage layer 34 can be determined as appropriate but isfavorably a metal material including at least one of Co, Fe, and Ni as amain component or a boron alloy including at least one of Co, Fe, and Niand B, for example. As an example, the second ferromagnetic layer 341can be formed of CoFeB similar to the first ferromagnetic layer 321, butcan also be formed of CoFeHf, CoFeW, CoFeTa, CoFeZr, CoFeNb, CoFeMo,CoFeNi, CoFeV, CoFeCr, CoFeNi, or the like.

Further, an accessory component may be added to the ferromagneticsubstance forming the second ferromagnetic layer 341 of the storagelayer 34 as necessary. By this addition of an accessory component, animprovement of heat resistance, an enhancement of a magnetoresistanceeffect, an improvement of a dielectric strength voltage, and the likecan be obtained. Examples of such an accessory component includeelemental substances, alloys, and oxides of B, C, N, O, F, Li, Mg, Si,P, Ti, V, Cr, Mn, Ni, Cu, Ge, Nb, Ru, Rh, Pd, Ag, Ta, Ir, Pt, Au, Zr,Hf, W, Mo, Re, and Os. Further, the second ferromagnetic layer 341 mayinclude a configuration in which a plurality of layers respectivelyformed of different types of ferromagnetic substances are directlylaminated on top of one another.

The heat generation layer 342 of the storage layer 34 includes a firstfunction of lowering power consumption in a recording operation of thestorage device 3 while maintaining an information retention property ofthe storage device 3, and a second function of suppressing an influenceof a heat load on the perpendicular magnetization M34 of the secondferromagnetic layer 341. Details of the heat generation layer 342 willbe given later.

(Intermediate Layer)

The intermediate layer 33 is formed of a nonmagnetic insulator and isarranged between the fixed layer 32 and the storage layer 34. Theintermediate layer 33 is configured as a tunnel barrier layer of the MTJdevice. In other words, in the storage device 3, as a voltage is appliedin the Z-axis direction, a current flows in the intermediate layer 33 bya tunnel effect, and electrons having a spin torque in a certaindirection are injected into the second ferromagnetic layer 341 of thestorage layer 34.

In the storage device 3, a necessary current for inverting theperpendicular magnetization M34 of the second ferromagnetic layer 341 ofthe storage layer 34 becomes lower as the magnetoresistance change rate(MR ratio) becomes larger, so it becomes possible to realize low powerconsumption. In the storage device 3, a magnesium oxide (MgO) is used asthe intermediate layer 33 for realizing a large MR ratio. It isfavorable for the MgO film configuring the intermediate layer 33 to becrystallized and to have a crystalline orientation of (001).

It is favorable for the film thickness of the intermediate layer 33 tobe determined such that an area resistance value becomes several tenΩμm² or less, for securing a sufficient current density for invertingthe perpendicular magnetization M34 of the second ferromagnetic layer341 of the storage layer 34. For example, in a case where theintermediate layer 33 is an MgO film, it is favorable for theintermediate layer 33 to have a thickness of 1.5 nm or less.

It should be noted that the material forming the intermediate layer 33may be materials other than MgO and may be, for example, variousinsulators, derivatives, and semiconductors such as Al₂O₃, AlN, SiO₂,Bi₂O₃, MgF₂, CaF, SrTiO₂, AlLa₃, Al—N—O, and MgAl₂O₄.

(Base Layer)

The base layer 31 is arranged below the fixed layer 32 in the Z-axisdirection. The base layer 31 includes a function as an electrode of theMTJ device, a function of controlling crystals of the fixed layer 32,and the like.

The base layer 31 can be configured as a layer that includes any one ofTa, Ti, Cu, TiN, TaN, NiCr, NiFeCr, Ru, and Pt as a main component, forexample. It is favorable for the base layer 31 to be configured by aplurality of layers respectively formed of different materials. As anexample, the base layer 31 may be configured by two layers including alayer formed of Ru and a layer formed of Ta.

(Cap Layer)

The cap layer 35 is arranged above the storage layer 34 in the Z-axisdirection. The cap layer 35 covers an upper surface of the storage layer34 in the Z-axis direction and includes a function of preventingoxidization of the storage layer 34 and the like.

The cap layer 35 can be configured as a metal layer including any one ofHf, Ta, W, Zr, Nb, Mo, Ti, Mg, V, Cr, Ru, Rh, Pd, and Pt as a maincomponent, for example. Alternatively, the cap layer 35 may include alaminated structure configured by the metal layer and an oxide layerincluding any one of MgO, Al₂O₃, and SiO₂ as a main component. Otherthan those described above, the material forming the oxide layer may be,for example, TiO₂, Bi₂O₃, SrTiO₂, AlLaO₃, Al—N—O, MgAl₂O₄, or the like.

(Other Configurations)

The storage device 3 may include configurations other than thosedescribed above. For example, the storage device 3 may include a hardmask layer arranged above the cap layer 35 in the Z-axis direction. Thehard mask layer can be formed of, for example, Ti, W, Ta, TiN, TaN, orthe like. It should be noted that the hard mask layer may be provided inplace of the cap layer 35.

[Heat Generation Layer]

(Schematic Configuration)

As shown in FIG. 3, the heat generation layer 342 of the storage layer34 is adjacent to the second ferromagnetic layer 341 on a lower side inthe Z-axis direction. The heat generation layer 342 is formed of aresistance heating element. The heat generation layer 342 mainlyincludes a first function and a second function described below. It isfavorable for the heat generation layer 342 to have a thickness thatfalls within a range of 0.2 nm or more and 2.0 nm or less for favorablyexhibiting the first function and the second function.

(First Function)

The first function of the heat generation layer 342 of the storage layer34 is to lower power consumption in a recording operation of the storagedevice 3 while maintaining the information retention property of thestorage device 3.

In general, the information retention property of the storage device 3,that is, the stability of the perpendicular magnetization M34 of thesecond ferromagnetic layer 341 of the storage layer 34, is expressed byΔ in Expression (1) below.

$\begin{matrix}\lbrack {{Expression}{\mspace{11mu} \;}1} \rbrack & \; \\{\Delta = {\frac{KV}{k_{B}T} = \frac{MsVHk}{2k_{B}T}}} & (1)\end{matrix}$

In Expression (1), K represents anisotropic energy, V represents avolume of the second ferromagnetic layer 341, K_(B) represents aBoltzmann constant, Ms represents a saturation magnetization amount, Hkrepresents an effective anisotropy field, and T represents a temperatureof the second ferromagnetic layer 341. Various elements such as amagnetic shape anisotropy, an induced magnetic anisotropy, and a crystalmagnetic anisotropy are incorporated in the effective anisotropy fieldHk, and the effective anisotropy field Hk becomes equivalent to amagnetic coercive force in a case where a single-domain simultaneousrotation model is presumed.

It is evaluated that, as the information retention property Δ expressedin Expression (1) becomes larger, the stability of the perpendicularmagnetization M34 of the second ferromagnetic layer 341 becomes higher.Conversely, it is evaluated that, as the information retention propertyΔ becomes smaller, the stability of the perpendicular magnetization M34of the second ferromagnetic layer 341 becomes lower. The storage device3 is configured such that the information retention property Δ becomessufficiently large in an ambient temperature (typically, roomtemperature) and is capable of favorably retaining recorded information.

On the other hand, as the information retention property Δ becomeslarger, the stability of the perpendicular magnetization M34 of thesecond ferromagnetic layer 341 becomes higher, and it becomes difficultfor the perpendicular magnetization M34 of the second ferromagneticlayer 341 to be inverted. Accordingly, a large current becomes necessaryfor inverting the perpendicular magnetization M34 of the secondferromagnetic layer 341 in the recording operation, so power consumptionduring the recording operation increases. In this regard, in the storagedevice 3, power consumption during the recording operation is lowered bylowering the information retention property Δ only for a moment duringthe recording operation by an operation of the heat generation layer342.

More specifically, as a spin injection is performed on the storagedevice 3, a current flows in the heat generation layer 342 formed of aresistance heating element to generate Joule heat. By this Joule heat,the temperature of the second ferromagnetic layer 341 adjacent to theheat generation layer 342 increases. In other words, in the storagedevice 3, the temperature of the second ferromagnetic layer 341 risesonly for a moment during the recording operation.

Here, referring to Expression (1), it can be seen that since theinformation retention property Δ is proportional to a reciprocal numberof the temperature T of the second ferromagnetic layer 341, theinformation retention property Δ becomes smaller as the temperature T ofthe second ferromagnetic layer 341 becomes higher. In other words, inthe storage device 3, by the temperature of the second ferromagneticlayer 341 rising only for a moment during the recording operation, theinformation retention property Δ becomes small, and the stability of theperpendicular magnetization M34 of the second ferromagnetic layer 341 islowered. Therefore, since the perpendicular magnetization M34 of thesecond ferromagnetic layer 341 can be inverted by a small current duringthe recording operation in the storage device 3, power consumption inthe recording operation can be reduced.

Further, since the temperature of the second ferromagnetic layer 341returns to the ambient temperature right after the recording operationin the storage device 3, a sufficiently-large information retentionproperty Δ is maintained except for that moment in the recordingoperation. In this way, in the storage device 3, power consumption inthe recording operation can be reduced without impairing the informationretention property Δ, due to the operation of the heat generation layer342.

(Second Function)

It is generally known that in the MTJ device, a property is largelydeteriorated by a heat load of 350° C. or more. Specifically, in somecases, a perpendicular magnetic anisotropy of the ferromagnetic layers(first ferromagnetic layer 321 and second ferromagnetic layer 341 inthis embodiment) included in the MTJ device may be eliminated by theheat load of 350° C. or more so that it becomes impossible to recordinformation by inversion of the perpendicular magnetizations.

In contrast, the second function of the heat generation layer 342 of thestorage layer 34 is to suppress the influence of a heat load on theperpendicular magnetization M34 of the second ferromagnetic layer 341.Specifically, also in a case where a heat load is applied to the storagedevice 3 in the production process of the storage apparatus 20, theprocessing of mounting the storage apparatus 20 to various electronicapparatuses, and the like, the perpendicular magnetization M34 of thesecond ferromagnetic layer 341 is less likely to be impaired.

More specifically, the heat generation layer 342 of the storage layer 34includes high heat resistance since it is formed of a resistance heatingelement, and even when a heat load is applied thereto, physical andchemical changes are less likely to occur. By providing the heatgeneration layer 342 including high heat resistance in the storagedevice 3, the perpendicular magnetization M34 of the secondferromagnetic layer 341 adjacent to the heat generation layer 342 isless likely to be influenced by the heat load. Accordingly, the magneticanisotropy of the MTJ device is maintained favorably, and highreliability as the storage device 3 can thus be obtained.

Specifically, the temperature of the storage device 3 may rise up toabout 400° C. in a CVD (Chemical Vapor Deposition) process in theproduction of the storage apparatus 20. Also in a case where such asituation is assumed and the storage device 3 is subjected to 3 hours ofheat processing at 400° C., it was confirmed that the perpendicularmagnetization M34 of the second ferromagnetic layer 341 is not impaireddue to the operation of the heat generation layer 342.

(Resistance Heating Element Forming Heat Generation Layer)

As the resistance heating element for forming the heat generation layer342, a material that is capable of appropriately raising a temperatureof the second ferromagnetic layer 341 by Joule heat and includes heatresistance that operates so as not to impair the perpendicularmagnetization M34 of the second ferromagnetic layer 341 can be adopted.As such a resistance heating element, a nitride, carbide, boride, oxide,elemental carbon, or elemental boron can be selected, for example.

More specifically, as the resistance heating element, for example, TiN,ZrN, HfN, VN, NbN, TaN, CrN, MoN, WN, SiN, AlN, BN, TiC, ZrC, HfC, VC,NbC, TaC, Cr₃C₂, Mo₂C, WC, SiC, AlC, B₄C, TiB₂, ZrB₂, HfB₂, VB₂, NbB₂,TaB₂, CrB₂, Mo₂B₅, W₂B, B₂O₃, B, C, and the like can be used as anelemental substance or a mixture thereof.

It is favorable to configure the resistance heating element by amaterial including an electrical resistivity of 1 Ωm or more and 1*10⁴Ωm or less at 20° C. from the viewpoint of appropriately raising thetemperature of the second ferromagnetic layer 341. The resistanceheating element may be configured by a single type of material includingthe electrical resistivity as described above, or an electricalresistivity of a compound material obtained by mixing a plurality oftypes of materials may be adjusted to the electrical resistivity asdescribed above. It should be noted that the electrical resistivity ofthe resistance heating element may either be a property value obtainedbefore deposition or a property value obtained after deposition.

Modified Example 1

FIG. 4 is a cross-sectional diagram schematically showing the storagedevice 3 according to Modified Example 1. In the storage device 3according to this modified example, a heat generation layer 322 isprovided not only in the storage layer 34 but also in the fixed layer32. The heat generation layer 322 is arranged below the firstferromagnetic layer 321 in the Z-axis direction. The heat generationlayer 322 of the fixed layer 32 includes functions similar to those ofthe heat generation layer 342 of the storage layer 34.

Specifically, although the heat generation layer 322 of the fixed layer32 is farther away from the second ferromagnetic layer 341 than the heatgeneration layer 342 of the storage layer 34, the heat generation layer322 generates Joule heat during a recording operation of the storagedevice 3 and facilitates temperature raise of the second ferromagneticlayer 341. Accordingly, power consumption in the recording operation ofthe storage device 3 can be reduced more effectively.

Further, by providing the heat generation layer 322 including heatresistance also in the fixed layer 32 in the storage device 3 accordingto this modified example, the perpendicular magnetization M32 of thefirst ferromagnetic layer 321 adjacent to the heat generation layer 322is also less likely to be influenced by a heat load. In other words,both the perpendicular magnetization M32 of the first ferromagneticlayer 321 and the perpendicular magnetization M34 of the secondferromagnetic layer 341 are less likely to be influenced by the heatload. Accordingly, the magnetic anisotropy of the MTJ device ismaintained favorably, and higher reliability as the storage device 3 canthus be obtained.

It should be noted that the positions of the second ferromagnetic layer341 and heat generation layer 342 in the storage layer 34 and thepositions of the first ferromagnetic layer 321 and heat generation layer322 in the fixed layer 32 may be set to be opposite from those of theconfiguration shown in FIG. 4. In other words, the heat generation layer342 may be arranged above the second ferromagnetic layer 341 in theZ-axis direction in the storage layer 34, and the heat generation layer322 may be arranged above the first ferromagnetic layer 321 in theZ-axis direction in the fixed layer 32.

Modified Example 2

FIG. 5 are cross-sectional diagrams each schematically showing thestorage layer 34 according to Modified Example 2. The storage layer 34according to this modified example includes, in addition to the heatgeneration layer 342 similar to that of the embodiment above, two secondferromagnetic layers 341U and 341L and a nonmagnetic layer 343. Thenonmagnetic layer 343 is arranged between the two second ferromagneticlayers 341U and 341L.

The second ferromagnetic layers 341U and 341L can both be formed of aferromagnetic substance similar to that of the second ferromagneticlayer 341 according to the embodiment above and can be formed of, forexample, Fe, Co, FeNi, CoFe, CoFeB, FeB, CoB, and the like. Theferromagnetic substances forming the two second ferromagnetic layers341U and 341L may also mutually differ. The nonmagnetic layer 343 can beformed of an elemental substance, alloy, oxide, and nitride of V, Cr,Nb, Mo, Ta, W, Hf, Zr, Ti, Ru, and Mg, for example.

The position of the heat generation layer 342 differs in theconfigurations of the storage layer 34 shown in FIGS. 5(A) to 5(D).

Specifically, in the configuration shown in FIG. 5(A), the heatgeneration layer 342 is adjacent to the lower side of the lower-sidesecond ferromagnetic layer 341L in the Z-axis direction.

In the configuration shown in FIG. 5(B), the heat generation layer 342is adjacent to the upper side of the upper-side second ferromagneticlayer 341U in the Z-axis direction.

In the configuration shown in FIG. 5(C), the heat generation layer 342is adjacent to the upper side of the lower-side second ferromagneticlayer 341L in the Z-axis direction.

In the configuration shown in FIG. 5(D), the heat generation layer 342is adjacent to the lower side of the upper-side second ferromagneticlayer 341U in the Z-axis direction.

In any of the configurations shown in FIGS. 5(A) to 5(D), the heatgeneration layer 342 can exert functions similar to those of theembodiment above.

It should be noted that the storage layer 34 may include a plurality ofheat generation layers 342. Specifically, the heat generation layers 342may be arranged at both the position adjacent to the lower-side secondferromagnetic layer 341L and the position adjacent to the upper-sidesecond ferromagnetic layer 341U.

Modified Example 3

FIG. 6 are cross-sectional diagrams each schematically showing the fixedlayer 32 according to Modified Example 3. The fixed layer 32 accordingto this modified example includes, in addition to the heat generationlayer 322 similar to that of Modified Example 1 above, two firstferromagnetic layers 321U and 321L and a nonmagnetic layer 323. Thenonmagnetic layer 323 is arranged between the two first ferromagneticlayers 321U and 321L.

The fixed layer 32 according to this modified example includes aso-called laminated ferrimagnetic structure. Directions of theperpendicular magnetizations M32 of the two first ferromagnetic layers321U and 321L of the fixed layer 32 are opposite to each other, that is,antiparallel. In the examples shown in FIG. 6, the lower-side firstferromagnetic layer 321L faces downward in the Z-axis direction, and theupper-side first ferromagnetic layer 321U faces upward in the Z-axisdirection. By setting the directions of the perpendicular magnetizationsM32 of the two first ferromagnetic layers 321U and 321L to be oppositeto each other in this way, a leak field in the fixed layer 32 can besuppressed to thus prevent the storage layer 34 from being influenced bythe leak field.

The two first ferromagnetic layers 321U and 321L can be formed of amaterial including at least one of Co, Fe, and Ni and at least one ofPt, Pd, Rh, and Ni as main components and can be formed of, for example,CoPt or FePt. The ferromagnetic substances forming the two firstferromagnetic layers 321U and 321L may also mutually differ. It shouldbe noted that at least one of the two first ferromagnetic layers 321Uand 321L may be formed of a material similar to that of the firstferromagnetic layer 321 according to the embodiment above, such as Fe,Co, FeNi, CoFe, CoFeB, FeB, and CoB.

The nonmagnetic layer 323 can be formed of an elemental substance oralloy of Ru, Os, Re, Ir, Au, Ag, Cu, Al, Bi, Si, B, C, Cr, Ta, Pd, Pt,Zr, Hf, W, Mo, Nb, V, and Ti, for example.

The position of the heat generation layer 322 differs in theconfigurations of the fixed layer 32 shown in FIGS. 6(A) to 6(D).

Specifically, in the configuration shown in FIG. 6(A), the heatgeneration layer 322 is adjacent to the lower side of the lower-sidefirst ferromagnetic layer 321L in the Z-axis direction.

In the configuration shown in FIG. 6(B), the heat generation layer 322is adjacent to the upper side of the upper-side first ferromagneticlayer 321U in the Z-axis direction.

In the configuration shown in FIG. 6(C), the heat generation layer 322is adjacent to the upper side of the lower-side first ferromagneticlayer 321L in the Z-axis direction.

In the configuration shown in FIG. 6(D), the heat generation layer 322is adjacent to the lower side of the upper-side first ferromagneticlayer 321U in the Z-axis direction.

In any of the configurations shown in FIGS. 6(A) to 6(D), the heatgeneration layer 322 can exert functions similar to those of ModifiedExample 1 above.

It should be noted that the fixed layer 32 may include a plurality ofheat generation layers 322. Specifically, the heat generation layers 322may be arranged at both the position adjacent to the lower-side firstferromagnetic layer 321L and the position adjacent to the upper-sidefirst ferromagnetic layer 321U.

Further, the fixed layer 32 may include a configuration that uses anantiferromagnetic layer or a soft magnetic layer. The antiferromagneticlayer can be formed of, for example, FeMn, PtMn, PtCrMn, NiMn, IrMn,NiO, Fe₂O₃, and the like. Moreover, regarding the two firstferromagnetic layers 321U and 321L, various physical properties such asa magnetic property, a crystalline structure, a crystalline property,and a stability can be adjusted by adding nonmagnetic elements such asAg, Cu, Au, Al, Si, Bi, Ta, B, C, O, N, Pd, Pt, Zr, Ta, Hf, Ir, W, Mo,and Nb.

Modified Example 4

FIG. 7 is a cross-sectional diagram schematically showing the storagedevice 3 according to Modified Example 4. The fixed layer 32 accordingto this modified example is divisionally provided above and below thestorage layer 34 in the Z-axis direction. Specifically, the upper-sidefirst ferromagnetic layer 321U is provided above the storage layer 34 inthe Z-axis direction, and the lower-side first ferromagnetic layer 321Lis provided below the storage layer 34 in the Z-axis direction. Theperpendicular magnetizations M32 of the two first ferromagnetic layers321U and 321L of the fixed layer 32 face mutually opposite directions.

Also in the storage device 3 according to this modified example, twointermediate layers 33U and 33L are provided in correspondence with thefirst ferromagnetic layers 321U and 321L that are provided divisionally.Specifically, the intermediate layer 33U is provided between the firstferromagnetic layer 321U and the storage layer 34, and the intermediatelayer 33L is provided between the first ferromagnetic layer 321L and thestorage layer 34. The configuration of this modified example also bearseffects similar to those of the embodiment above.

It should be noted that the fixed layer 32 of the storage device 3according to this modified example may include the heat generation layer322. Specifically, the heat generation layer 322 may be arranged at atleast one of the position adjacent to the lower-side first ferromagneticlayer 321L and the position adjacent to the upper-side firstferromagnetic layer 321U.

[Evaluation of Storage Device]

(Magnetic Property)

For confirming the operation of the heat generation layer 342 in thestorage device 3, the magnetic property was evaluated in samples S11 andS12 having configurations in which the fixed layer 32 is not provided inthe storage device.

FIG. 8(A) is a cross-sectional diagram schematically showing the sampleS11, and FIG. 8(B) is a cross-sectional diagram schematically showingthe sample S12. The samples S11 and S12 are both configured by the baselayer 31, the intermediate layer 33, the storage layer 34, and the caplayer 35. The sample S11 includes the heat generation layer 342, and thesample S12 does not include the heat generation layer 342. Theconfiguration excluding the heat generation layer 342 is common to thesamples S11 and S12. Therefore, by comparing the samples S11 and S12,the operation of the heat generation layer 342 with respect to themagnetic property of the storage layer 34 can be confirmed.

As the common configuration of the samples S11 and S12, the base layer31 is configured as a laminated film constituted of a Ta layer 312having a film thickness of 5.0 nm and an Ru layer 311 having a filmthickness of 5.0 nm.

The intermediate layer 33 is configured as an MgO film having a filmthickness of 1.0 nm.

The second ferromagnetic layer 341 of the storage layer 34 is configuredas a CoFeB film having a film thickness of 1.5 nm.

The cap layer 35 is configured as a Ta film having a film thickness of5.0 nm.

The heat generation layer 342 of the sample S11 is configured as aresistance heating element film having a film thickness of 0.2 nm. Theheat generation layer 342 was formed by a resistance heating elementthat is configured by at least one of a nitride, carbide, boride, oxide,elemental carbon, and elemental boron and includes an electricalresistivity of 1 Ωm or more and 1*10⁴ Ωm or less at 20° C.

After subjecting the prepared samples S11 and S12 to heat processing at400° C. for 3 hours, the magnetic properties were measured.

FIG. 9 are diagrams showing measurement results of the magnetic propertyof the sample S11. FIG. 9(A) is a graph showing a result of amagneto-optical effect (MOKE: Magneto-optical Kerr Effect) measurement,and FIG. 9(B) is a graph showing a measurement result obtained by avibrating sample magnetometer (VSM: Vibrating Sample Magnetometer: VSM).

As shown in FIG. 9(A), in the sample S11, a rectangular MOKE waveform ofa high aspect ratio, that indicates an extremely-clear perpendicularmagnetic anisotropy, was obtained by the MOKE measurement. Further, asshown in FIG. 9(B), in the sample S11, a waveform indicating asufficiently-large perpendicular magnetic anisotropy was obtained alsoin the measurement using the VSM. Accordingly, it was confirmed thatalso after the heat processing at 400° C. for 3 hours, the perpendicularmagnetization M34 of the second ferromagnetic layer 341 of the storagelayer 34 was maintained favorably in the sample S11.

FIG. 10 is a graph showing a VSM measurement result on the sample S12.As shown in FIG. 10, it can be seen that in the sample S12, a waveformindicating a perpendicular magnetic anisotropy is not obtained in theVSM measurement and that the perpendicular magnetic anisotropy is lost.Accordingly, it was confirmed that in the sample S12, the perpendicularmagnetization M34 of the second ferromagnetic layer 341 of the storagelayer 34 is lost by the heat processing at 400° C. for 3 hours.

By the above comparison of the samples S11 and S12, it was confirmedthat the perpendicular magnetization M34 of the second ferromagneticlayer 341 of the storage layer 34 is favorably maintained in the sampleS11 by the operation of the heat generation layer 342.

(Information Retention Property Δ and Information Writing CurrentDensity Jc0)

For confirming the operation of the heat generation layer 342 in thestorage device 3, the information retention property Δ and informationwriting current density Jc0 of samples S21 and S22 of the storage devicewere evaluated.

FIG. 11(A) is a cross-sectional diagram schematically showing the sampleS21, and FIG. 11(B) is a cross-sectional diagram schematically showingthe sample S22. The samples S21 and S22 were each formed on athermally-oxidized film that has a thickness of 300 nm and is providedon a silicon substrate having a thickness of 0.725 mm.

The samples S21 and S22 are both configured by the base layer 31, thefixed layer 32, the intermediate layer 33, the storage layer 34, and thecap layer 35. The sample S21 includes the heat generation layer 342, andthe sample S22 does not include the heat generation layer 342. Theconfiguration excluding the heat generation layer 342 is common to thesamples S21 and S22. Therefore, by comparing the samples S21 and S22,the operation of the heat generation layer 342 with respect to theinformation retention property Δ and information writing current densityJc0 can be confirmed.

As the common configuration of the samples S21 and S22, the base layer31 is configured as a laminated film constituted of a Ta layer 312having a film thickness of 5.0 nm and an Ru layer 311 having a filmthickness of 5.0 nm.

The fixed layer 32 includes a laminated ferrimagnetic structureconstituted of the first ferromagnetic layer 321 that is formed of CoPtand has a film thickness of 2.5 nm, the nonmagnetic layer 323 that isformed of Ru and has a film thickness of 0.8 nm, and first ferromagneticlayer 321 that is formed of CoPt and has a film thickness of 2.5 nm.

The intermediate layer 33 is configured as an MgO film having a filmthickness of 1.0 nm.

The second ferromagnetic layer 341 of the storage layer 34 is configuredas a CoFeB film having a film thickness of 1.5 nm.

The cap layer 35 is configured as a laminated film constituted of a Tafilm 351 having a film thickness of 3.0 nm, an Ru film 352 having a filmthickness of 3.0 nm, and a Ta film 351 having a film thickness of 3.0nm.

The heat generation layer 342 of the sample S21 is configured as aresistance heating element film having a film thickness of 0.2 nm. Theheat generation layer 342 was formed by a resistance heating elementthat is configured by at least one of a nitride, carbide, boride, oxide,elemental carbon, and elemental boron and includes an electricalresistivity of 1 Ωm or more and 1*10⁴ Ωm or less at 20° C.

The prepared samples S21 and S22 were subjected to first heat processingat 350° C. for 1 hour and second heat processing at 400° C. for 3 hours.After each of the heat processing, the information retention property Δand information writing current density Jc0 were obtained for each ofthe samples S21 and S22. The information retention property Δ wascalculated from a result of a temperature acceleration retention test.The information writing current density Jc0 was calculated from a pulsewidth dependency of a magnetization inversion current Ic. Table 1 showsthe information retention property Δ and information writing currentdensity Jc0 of the samples S21 and S22 obtained after each of the heatprocessing.

TABLE 1 Sample S21 Sample S22 After 1st After 2nd After 1st After 2ndheat heat heat heat processing processing processing processing (350°C./1 (400° C./3 (350° C./1 (400° C./3 hour) hours) hour) hours) Δ 65 6238 — Jc0 [a.u.] 0.8 0.8 1.0 —

As shown in Table 1, the information retention property Δ obtained afterthe first heat processing was 38 in the sample S22 whereas it was 65 inthe sample S21. Accordingly, it can be seen that, by the operation ofthe heat generation layer 342, the information retention property Δobtained after the first heat processing largely increases so that theperpendicular magnetization M34 of the second ferromagnetic layer 341 ofthe storage layer 34 is less likely to be impaired.

On the other hand, the information writing current density Jc0 obtainedafter the first heat processing was 1.0 in the sample S22 whereas it was0.8 in the sample S21. Accordingly, it can be seen that the informationwriting current density Jc0 is reduced 20% by the operation of the heatgeneration layer 342.

By the above comparison of the samples S21 and S22 after the first heatprocessing, it was confirmed that the information retention property Δof the storage device is improved and power consumption in the recordingoperation of the storage device is reduced by the operation of the heatgeneration layer 342.

Further, in the sample S21, the information retention property Δ andinformation writing current density Jc0 equivalent to those obtainedafter the first heat processing were obtained also after the second heatprocessing. On the other hand, in the sample S22 after the second heatprocessing, the perpendicular magnetic anisotropy was lost, and theinformation retention property Δ and information writing current densityJc0 were not obtained.

From the results described above, it was confirmed that in the sampleS21, both the information retention property A and the informationwriting current density Jc0 are not impaired due to the operation of theheat generation layer 342 even after the first heat processing at 350°C. for 1 hour and the second heat processing at 400° C. for 3 hours.

[Application Example of Storage Device]

The storage device 3 according to the embodiment above is applicable tonot only the storage apparatus 20 but also a magnetic head, variouselectronic apparatuses, and the like. Hereinafter, as an example ofthis, a magnetic head including the storage device 3 and an electronicapparatus including the storage device 3 will be described.

(Magnetic Head)

FIG. 12 are diagrams schematically showing a compound magnetic head 100.FIG. 12(A) is a perspective view of the compound magnetic head 100, andFIG. 12(B) is a cross-sectional diagram of the compound magnetic head100. In FIG. 12(A), the compound magnetic head 100 is partially notchedto help understand an internal structure thereof. The compound magnetichead 100 includes a magneto-sensitive device 101 which is a magneticdevice including a laminated structure having a configuration similar tothat of the storage device 3 according to the embodiment above.

The compound magnetic head 100 can be used in a hard disk apparatus, forexample. The compound magnetic head 100 includes a substrate 122 and amagnetoresistance-effect-type magnetic head formed on the substrate 122.The compound magnetic head 100 also includes an inductive-type magnetichead laminated on the magnetoresistance-effect-type magnetic head.

In the compound magnetic head 100, the magnetoresistance-effect-typemagnetic head functions as a reproduction head, and the inductive-typemagnetic head functions as a recording head. In other words, thecompound magnetic head 100 includes a configuration in which thereproduction head and the recording head are combined.

The magnetoresistance-effect-type magnetic head of the compound magnetichead 100 is a so-called shield-type MR head. Themagnetoresistance-effect-type magnetic head includes a first magneticshield 125, the magneto-sensitive device 101, and a second magneticshield 127. The first magnetic shield 125 is formed on the substrate 122via an insulation layer 123. The magneto-sensitive device 101 is formedon the first magnetic shield 125 via the insulation layer 123. Thesecond magnetic shield 127 is formed on the magneto-sensitive device 101via the insulation layer 123.

The insulation layer 123 is formed of an insulation material such asAl₂O₃ and SiO₂, for example. The first magnetic shield 125 is formed ofa soft magnetic substance such as Ni—Fe and magnetically shields a lowerlayer side of the magneto-sensitive device 101, for example. Similarly,the second magnetic shield 127 magnetically shields an upper layer sideof the magneto-sensitive device 101.

In the magnetoresistance-effect-type magnetic head, themagneto-sensitive device 101 detects magnetic signals from a magneticrecording medium. The magneto-sensitive device 101 is substantiallyrectangular, and one side surface thereof is exposed to an opposingsurface of the magnetic recording medium. Bias layers 128 and 129 areconnected to both ends of the magneto-sensitive device 101, andconnection terminals 130 and 131 are further connected to the biaslayers 128 and 129. With such a configuration, a sense current can besupplied to the magneto-sensitive device 101 via the connectionterminals 130 and 131.

The inductive-type magnetic head of the compound magnetic head 100includes a magnetic core and a thin-film coil 133. The magnetic core isconfigured by the second magnetic shield 127 and an upper-layer core132. The thin-film coil 133 is formed so as to be wound around themagnetic core.

The upper-layer core 132 configuring the magnetic core is formed of asoft magnetic substance such as Ni—Fe, for example, and forms a closedmagnetic path with the second magnetic shield 127. Front end portions ofthe second magnetic shield 127 and the upper-layer core 132 are setapart so as to form a predetermined gap g, and both are exposed to theopposing surface of the magnetic recording medium. The gap g between thesecond magnetic shield 127 and the upper-layer core 132 configures arecording magnetic gap of the inductive-type magnetic head. The secondmagnetic shield 127 and the upper-layer core 132 are connected at rearend portions thereof.

The thin-film coil 133 embedded in the insulation layer 123 is formedbetween the second magnetic shield 127 and the upper-layer core 132. Thethin-film coil 133 is formed so as to be wound around the magnetic coreconstituted of the second magnetic shield 127 and the upper-layer core132 in an in-plane direction. Although not shown in FIG. 12, terminalsare provided at both end portions of the thin-film coil 133. Each of theterminals of the thin-film coil 133 is externally exposed and configuresan external connection terminal of the inductive-type magnetic head. Inother words, by supplying a recording current to each of the terminalsof the thin-film coil 133, magnetic signals can be recorded onto themagnetic recording medium.

Since the magneto-sensitive device 101 of the compound magnetic head 100includes a configuration similar to that of the storage device 3according to the embodiment above, both a high information retentionproperty Δ and low power consumption are realized. In other words, it ispossible to perform more-accurate reproduction operations by low powerconsumption in the compound magnetic head 100 equipped with themagneto-sensitive device 101.

(Electronic Apparatus)

FIG. 13 is a block diagram showing a schematic configuration of anelectronic apparatus 200 including the storage device 3 or the storageapparatus 20 according to this embodiment. The electronic apparatus 200includes the storage device 3 or the storage apparatus 20 of thisembodiment as a storage unit 201. Examples of the electronic apparatus200 include various computers, a mobile terminal apparatus, a gameapparatus, a music apparatus, and a video apparatus.

The electronic apparatus 200 includes a control unit 202 capable ofaccessing the storage unit 201.

The electronic apparatus 200 may also include an input operation unit203, for example. In this case, the control unit 202 is capable ofrecording information corresponding to a content of a user operationwith respect to the input operation unit 203 in the storage unit 201.

Further, the electronic apparatus 200 may also include an informationpresentment unit 204 capable of displaying videos and reproducing audio,for example. The information presentment unit 204 is typicallyconfigured as a display apparatus, a speaker, or the like. In this case,the control unit 202 is capable of reading information recorded in thestorage unit 201 and displaying or reproducing the information by theinformation presentment unit 204 in response to a user request.

Heretofore, the embodiment of the present technology has been described.However, the present technology is not limited to the embodiment aboveand can of course be variously modified without departing from the gistof the present technology.

For example, although the example where the fixed layer is providedbelow the storage layer in the Z-axis direction in the storage devicehas been described in the embodiment above, the positions of the storagelayer and the fixed layer in the storage device may become opposite. Asan example, the storage device may be of a so-called top laminatedferrimagnetic type in which the fixed layer of the laminatedferrimagnetic structure is provided above the storage layer in theZ-axis direction.

It should be noted that the present technology can also take thefollowing configurations.

(1) A storage device, including:

a fixed layer including a first ferromagnetic layer that includes afixed perpendicular magnetization;

a storage layer including a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection;

an intermediate layer that is formed of an insulator and is arrangedbetween the storage layer and the fixed layer; and

a heat generation layer that is formed of a resistance heating elementand is arranged in at least one of the storage layer and the fixedlayer.

(2) The storage device according to (1), in which

the heat generation layer is arranged in at least the storage layer.

(3) The storage device according to (1) or (2), in which

the heat generation layer is adjacent to the first ferromagnetic layeror the second ferromagnetic layer.

(4) The storage device according to any one of (1) to (3), in which

the resistance heating element is configured by at least one of anitride, carbide, boride, oxide, elemental carbon, and elemental boronand includes an electrical resistivity of 1 Ωm or more and 1*10⁴ Ωm orless at 20° C.

(5) The storage device according to any one of (1) to (4), in which

the heat generation layer has a thickness of 0.2 nm or more and 2.0 nmor less.

(6) The storage device according to any one of (1) to (5), in which

the first ferromagnetic layer and the second ferromagnetic layer areformed of a metal including at least one of Co, Fe, and Ni as a maincomponent or a boron alloy including at least one of Co, Fe, and Ni andB.

(7) The storage device according to (6), in which

the first ferromagnetic layer and the second ferromagnetic layer areformed of a material including at least one of V, Cr, Nb, Mo, Ta, W, Hf,Zr, Ti, and Ru as an accessory component.

(8) The storage device according to (1), in which

the fixed layer further includes two first ferromagnetic layers and anonmagnetic layer arranged between the two first ferromagnetic layers.

(9) The storage device according to (8), in which at least one of thetwo first ferromagnetic layers is formed of a material including atleast one of Co, Fe, and Ni and at least one of Pt, Pd, Rh, and Ni asmain components.(10) The storage device according to (9), in which one of the two firstferromagnetic layers is formed of a material including at least one ofCo, Fe, and Ni and at least one of Pt, Pd, Rh, and Ni as maincomponents, and

the other one of the two first ferromagnetic layers is formed of a metalincluding at least one of Co, Fe, and Ni as a main component or a boronalloy including at least one of Co, Fe, and Ni and B.

(11) The storage device according to any one of (1) to (10), in which

the insulator is configured by MgO.

(12) The storage device according to any one of (1) to (11), furtherincluding

a cap layer adjacent to the storage layer on a side opposite to theintermediate layer.

(13) The storage device according to (12), in which

the cap layer includes a metal layer including any one of Hf, Ta, W, Zr,Nb, Mo, Ti, Mg, V, Cr, Ru, Rh, Pd, and Pt as a main component.

(14) The storage device according to (13), in which the cap layerfurther includes an oxide layer including any one of MgO, Al₂O₃, andSiO₂ as a main component.(15) The storage device according to any one of (1) to (14), furtherincluding

a base layer adjacent to the fixed layer on a side opposite to theintermediate layer.

(16) The storage device according to (15), in which

the base layer includes a plurality of layers that include any one ofTa, Ti, Cu, TiN, TaN, NiCr, NiFeCr, Ru, and Pt as a main component.

(17) A storage apparatus, including:

a plurality of storage devices each including

-   -   a fixed layer including a first ferromagnetic layer that        includes a fixed perpendicular magnetization,    -   a storage layer including a second ferromagnetic layer that        includes a perpendicular magnetization invertible by a spin        injection,    -   an intermediate layer that is formed of an insulator and is        arranged between the storage layer and the fixed layer, and    -   a heat generation layer that is formed of a resistance heating        element and is arranged in at least one of the storage layer and        the fixed layer; and

a wiring unit configured to be capable of supplying a current to each ofthe plurality of storage devices.

(18) A magnetic head, including

a magnetic device including

-   -   a fixed layer including a first ferromagnetic layer that        includes a fixed perpendicular magnetization,    -   a storage layer including a second ferromagnetic layer that        includes a perpendicular magnetization invertible by a spin        injection,    -   an intermediate layer that is formed of an insulator and is        arranged between the storage layer and the fixed layer, and    -   a heat generation layer that is formed of a resistance heating        element and is arranged in at least one of the storage layer and        the fixed layer.        (19) An electronic apparatus, including:

a storage unit including

-   -   a plurality of storage devices each including        -   a fixed layer including a first ferromagnetic layer that            includes a fixed perpendicular magnetization,        -   a storage layer including a second ferromagnetic layer that            includes a perpendicular magnetization invertible by a spin            injection,        -   an intermediate layer that is formed of an insulator and is            arranged between the storage layer and the fixed layer, and        -   a heat generation layer that is formed of a resistance            heating element and is arranged in at least one of the            storage layer and the fixed layer; and

a control unit configured to be capable of accessing the storage unit.

REFERENCE SIGNS LIST

-   20 storage apparatus-   3 storage layer-   31 base layer-   32 fixed layer-   321 first ferromagnetic layer-   33 intermediate layer-   34 storage layer-   341 second ferromagnetic layer-   342 heat generation layer-   35 cap layer-   M32 perpendicular magnetization-   M34 perpendicular magnetization

1. A storage device, comprising: a fixed layer including a firstferromagnetic layer that includes a fixed perpendicular magnetization; astorage layer including a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection; anintermediate layer that is formed of an insulator and is arrangedbetween the storage layer and the fixed layer; and a heat generationlayer that is formed of a resistance heating element and is arranged inat least one of the storage layer and the fixed layer.
 2. The storagedevice according to claim 1, wherein the heat generation layer isarranged in at least the storage layer.
 3. The storage device accordingto claim 1, wherein the heat generation layer is adjacent to the firstferromagnetic layer or the second ferromagnetic layer.
 4. The storagedevice according to claim 1, wherein the resistance heating element isconfigured by at least one of a nitride, carbide, boride, oxide,elemental carbon, and elemental boron and includes an electricalresistivity of 1 Ωm or more and 1*10⁴ Ωm or less at 20° C.
 5. Thestorage device according to claim 1, wherein the heat generation layerhas a thickness of 0.2 nm or more and 2.0 nm or less.
 6. The storagedevice according to claim 1, wherein the first ferromagnetic layer andthe second ferromagnetic layer are formed of a metal including at leastone of Co, Fe, and Ni as a main component or a boron alloy including atleast one of Co, Fe, and Ni and B.
 7. The storage device according toclaim 6, wherein the first ferromagnetic layer and the secondferromagnetic layer are formed of a material including at least one ofV, Cr, Nb, Mo, Ta, W, Hf, Zr, Ti, and Ru as an accessory component. 8.The storage device according to claim 1, wherein the fixed layer furtherincludes two first ferromagnetic layers and a nonmagnetic layer arrangedbetween the two first ferromagnetic layers.
 9. The storage deviceaccording to claim 8, wherein at least one of the two firstferromagnetic layers is formed of a material including at least one ofCo, Fe, and Ni and at least one of Pt, Pd, Rh, and Ni as maincomponents.
 10. The storage device according to claim 9, wherein one ofthe two first ferromagnetic layers is formed of a material including atleast one of Co, Fe, and Ni and at least one of Pt, Pd, Rh, and Ni asmain components, and the other one of the two first ferromagnetic layersis formed of a metal including at least one of Co, Fe, and Ni as a maincomponent or a boron alloy including at least one of Co, Fe, and Ni andB.
 11. The storage device according to claim 1, wherein the insulator isconfigured by MgO.
 12. The storage device according to claim 1, furthercomprising a cap layer adjacent to the storage layer on a side oppositeto the intermediate layer.
 13. The storage device according to claim 12,wherein the cap layer includes a metal layer including any one of Hf,Ta, W, Zr, Nb, Mo, Ti, Mg, V, Cr, Ru, Rh, Pd, and Pt as a maincomponent.
 14. The storage device according to claim 13, wherein the caplayer further includes an oxide layer including any one of MgO, Al₂O₃,and SiO₂ as a main component.
 15. The storage device according to claim1, further comprising a base layer adjacent to the fixed layer on a sideopposite to the intermediate layer.
 16. The storage device according toclaim 15, wherein the base layer includes a plurality of layers thatinclude any one of Ta, Ti, Cu, TiN, TaN, NiCr, NiFeCr, Ru, and Pt as amain component.
 17. A storage apparatus, comprising: a plurality ofstorage devices each including a fixed layer including a firstferromagnetic layer that includes a fixed perpendicular magnetization, astorage layer including a second ferromagnetic layer that includes aperpendicular magnetization invertible by a spin injection, anintermediate layer that is formed of an insulator and is arrangedbetween the storage layer and the fixed layer, and a heat generationlayer that is formed of a resistance heating element and is arranged inat least one of the storage layer and the fixed layer; and a wiring unitconfigured to be capable of supplying a current to each of the pluralityof storage devices.
 18. A magnetic head, comprising a magnetic deviceincluding a fixed layer including a first ferromagnetic layer thatincludes a fixed perpendicular magnetization, a storage layer includinga second ferromagnetic layer that includes a perpendicular magnetizationinvertible by a spin injection, an intermediate layer that is formed ofan insulator and is arranged between the storage layer and the fixedlayer, and a heat generation layer that is formed of a resistanceheating element and is arranged in at least one of the storage layer andthe fixed layer.
 19. An electronic apparatus, comprising: a storage unitincluding a plurality of storage devices each including a fixed layerincluding a first ferromagnetic layer that includes a fixedperpendicular magnetization, a storage layer including a secondferromagnetic layer that includes a perpendicular magnetizationinvertible by a spin injection, an intermediate layer that is formed ofan insulator and is arranged between the storage layer and the fixedlayer, and a heat generation layer that is formed of a resistanceheating element and is arranged in at least one of the storage layer andthe fixed layer; and a control unit configured to be capable ofaccessing the storage unit.